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A238336 The first row of Pascal's triangle having exactly n distinct squarefree numbers, or -1 if no such row exists. 1
0, 2, 5, 7, 13, 11, 15, 44, 53, 46, 59, 23, 43, 278, 191, 143, 79, 119, 187, 62, 47, 221, 214, 1643, 159, 238, 95, 473, 314, 3583, 671, 474, 958, 3071, 5719, 215, 1439, 7423, 1663, 447, 223, 3695, 4346, 4318, 12983, 319, 35069, 5983, 5471, 8567, 959, 3067 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

LINKS

Table of n, a(n) for n=1..52.

A. Granville and O. Ramaré, Explicit bounds on exponential sums and the scarcity of squarefree binomial coefficients, Mathematika 43 (1996), 73-107, [DOI].

MATHEMATICA

nn = 20; t = Table[-1, {nn}]; found = 0; n = -1; While[found < nn, n++; len = Length[Select[Binomial[n, Range[0, n/2]], SquareFreeQ[#] &]]; If[0 < len <= nn && t[[len]] == -1, t[[len]] = n; found++]]; t

CROSSREFS

Cf. A064461, A238337.

Sequence in context: A041975 A042577 A092792 * A083271 A094285 A121218

Adjacent sequences:  A238333 A238334 A238335 * A238337 A238338 A238339

KEYWORD

nonn,more,hard

AUTHOR

T. D. Noe, Mar 05 2014

EXTENSIONS

Extended by T. D. Noe, Mar 07 2014

STATUS

approved

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Last modified August 24 03:20 EDT 2019. Contains 326260 sequences. (Running on oeis4.)